Can some body explain this query ...

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Actually i found this query from this link
http://use-the-index-luke.com/sql/where-clause/obfuscation/smart-logic[^]

SQL

SELECT first_name, last_name, subsidiary_id, employee_id
  FROM employees
 WHERE( subsidiary_id    = NULL     OR NULL IS NULL )
   AND( employee_id      = NULL     OR NULL IS NULL )
   AND( UPPER(last_name) = 'WINAND' OR 'WINAND' IS NULL )

Explain what does this mean " NULL IS NULL" and what is its functionality here ?Thanks

Posted 18-Nov-13 18:33pm

Member 8840306

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ArunRajendra 19-Nov-13 0:40am

there is a issue with the query. subsidiary_id = NULL should be IS null.

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_Damian S_ · Accepted Answer · 2013-11-18T18:38:00

Solution 1

NULL IS NULL will simply return true, hence that part of the where clause is completely pointless, as regardless what happens with the subsidiary_id field, the result of the OR will always be true.

Posted 18-Nov-13 18:38pm

_Damian S_